Add test to cover when unable to replace magics (#2471)

[etc/vim.git] / docs / faq.md

diff --git a/docs/faq.md b/docs/faq.md
index ac5ba937c1c2f4501dc7bb87428ba90687fb5048..c361addf7ae2b21b69ef1860824c1e02e12f0887 100644 (file)
--- a/docs/faq.md
+++ b/docs/faq.md
@@ -37,6 +37,29 @@ Most likely because it is ignored in `.gitignore` or excluded with configuration
 [file collection and discovery](usage_and_configuration/file_collection_and_discovery.md)
 for details.
 
+## Why is my Jupyter Notebook cell not formatted?
+
+_Black_ is timid about formatting Jupyter Notebooks. Cells containing any of the
+following will not be formatted:
+
+- automagics (e.g. `pip install black`)
+- multiline magics, e.g.:
+
+  ```python
+  %timeit f(1, \
+          2, \
+          3)
+  ```
+
+- code which `IPython`'s `TransformerManager` would transform magics into, e.g.:
+
+  ```python
+  get_ipython().system('ls')
+  ```
+
+- invalid syntax, as it can't be safely distinguished from automagics in the absence of
+  a running `IPython` kernel.
+
 ## Why are Flake8's E203 and W503 violated?
 
 Because they go against PEP 8. E203 falsely triggers on list